This invention relates generally to trucks and trailers of the type having a reciprocating floor system for transporting and off-loading loads of granular material, and more particularly to apparatus for minimizing the amount of residual granular material that remains on a reciprocating floor after the offloading process is completed.
Apparatus directed to assist in the unloading process of granular material loads from trucks are known in the art. Two early devices provided for this purpose are U.S. Pat. No. 2,033,209 issued to Teetor in 1935 that discloses a tiltable dumping unit mounted within a truck bed for receiving a material load, the dumping unit being tilted to remove the load. Similarly U.S. Pat. No. 3,826,534 issued Ruff in 1974 discloses a dump body pivotally placed within a truck body to receive a material load that is removed upon pivoting action of the dump body. These designs employ motorized mechanisms that must be powerful enough to lift and tilt the entire material load.
Several later designs incorporated various types of flexible belts or sheets that are wound around a reel to remove a material load. For example U.S. Pat. No. 3,978, 996 issued to Oltrogge 1976 discloses a flexible conveyor belt upon which a material load is placed, wherein the material is removed by a winch powered drum roller that pulls and reels the belt rearward thereby urging and removing the material load from the rear of the truck.
U.S. Pat. No. 4,277,220 issued to Wiley in 1981 discloses an unloader having a flexible apron that is wound rearwardly over a material load placed thereon by a winch to generate a rearward tumbling and conveying action on the load material to urge the same from the truck.
Similarly U.S. Pat. No. 4,629,390 issued to Burke in 1986 discloses a flexible conveyor sheet that is movable from an unwound position, from a rearwardly disposed drum to receive material, to a wound position around the drum to unload the material from the rear of the truck.
In 1992, U.S. Pat. No. 5,156,518 issued to VanMatre disclosing an unloading device comprising a movable frame for moving a sheet upon which a material load is placed. The movable frame moves the sheet from the rear of a truck bed toward the open gate thereof to remove the material load.
Each of these later designs require that a material load be mechanically moved responsive to movement of a sheet upon which the material load is placed. This type of action requires a relatively complex and powerful mechanical mechanism as well as expensive durable belts and/or sheets. None of the above noted inventions are directed to a simple, uncomplicated design arranged to take advantage of a truck's reciprocating floor, and that employs a flexible sheet that advances responsive to the load being moved.
Accordingly, a need remains for a simple inexpensive device for minimizing residual material from reciprocating floor type trucks that are used to transport and unload granular material.